Description
ABSTRACT
Knowledge of the thermal and electrical properties of a dry sandy soil is of great importance in agricultural meteorology where problems of heat exchange at the soil surface are encountered. The availability of these data is important because of the improvements in wider applications of soil heat and water transport models as well as seed germination and crop growth. This research work therefore intends to determine the variability of soil thermal and electrical properties of a seasonally cultivated Agricultural Teaching and Research Farm located within the University of Ibadan campus, South-western Nigeria with a view to have understanding of how different soils warm up in order to allow better planning of planting of crops.
TABLE OF CONTENTS
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENT
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the project
1.2 Problem Statement
1.3 Aim and objectives of the project
1.4 Significance of the project
1.5 Scope of the study
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 Review of the study
2.2 Basic Electrical Theory: Electric Current
2.3 Basic Electrical Theory: Electrical Resistance
2.4 Ohm’s Law
2.5 Electrical phenomena in soils
2.6 Geophysical methods for measuring electrical parameters in soils
2.6.1 Classification of Electrical methods
2.6.2 Self-potential method
2.6.3 Four-electrode probe
2.7 Soil Thermal Properties
2.7.1 Thermal Conductivity
- Heat Capacity
- Thermal Diffusivity
CHAPTER THREE
3.0 Materials and Method
3.1 STUDY AREA
3.2 Method Of The Study
3.3 Field Procedure
3.4 Labouratory Procedure
CHAPTER FOUR
4.0 Result and Discussion
CHAPTER FIVE
5.0 Conclusion
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Soil is a heterogeneous medium consisted of liquid, solid, and gaseous phases. The solid and liquid phases play an essential role in soil spontaneous electrical phenomena and in behavior of electrical fields, artificially created in soil.
Electrical and thermal conductivities are key properties for estimating soil physical states, subsurface water and energy balances, and land-atmosphere interactions. Soil bulk electrical measurements are affected by contact between soil and the measuring device or electrode because the flow of charge is through the liquid phase. The electrical is often used as a surrogate measurement across fields and watersheds to differentiate soil and management boundaries, without theoretical analysis of the chemical and physical properties that are actually being measured (Carroll and Oliver, 2015; McCutcheon et al., 2016; Harvey and Morgan, 2019). Many factors affect electrical properties, If aggregates are large in relation to the electrode, contact is affected in partially wetted soil; therefore, aggregate size can influence electrical properties measurements for certain water content ranges (Logsdon, 2016). In addition to soil structure, soil electrical properties is increased by high levels of soil solution concentration (Shainberg et al., 2010), water content, temperature, and high charge clays (Logsdon and Laird, 2014; Hunt et aI., 2016).
Soil thermal properties are required in many areas of engineering, agronomy, and soil science, and in recent years considerable effort has gone into developing techniques to determine these properties. The thermal properties of soil are one of the factors that determine mass and energy exchange that takes place in soil-plant-atmosphere system. The determination of these properties such as thermal conductivity, thermal diffusivity and volumetric heat capacity, and their variability is therefore a very important factor in understanding these processes at an individual scale of crop field and larger areas. The investigation of these thermal properties can have significant practical consequences such as evaluation of optimum conditions for plant growth and development and can also be utilized for the control of thermal-moisture regime of soil in the field (Usowicz, 2011). Seed germination, seedling emergence, and subsequent stand establishment are influenced by the microclimate. Thermal properties of soils play an important role in influencing microclimate (Ghuman and Lal, 2015). These properties influence how energy is partitioned in the soil profile. The ability to monitor soil thermal properties is an important tool in managing the soil temperature regime to affect seed germination and growth. While related to soil temperature, it is more accurately associated with the transfer of heat throughout the soil, by radiation, conduction and convection.
The use of a thermal probe called KD 2 Pro has made it possible to measure the thermal properties of soil (in-situ) as well as its spatial variability. Thermal properties and physical properties of soil in cultivated fields are modified by different treatments and crops. Hence the variability of thermal properties may be different for an individual field with the growth of a specific crop compared with a group of fields with different crops.
For the agriculture farm within the premises of University of Ibadan, information on thermal properties has been lacking. These data are needed for constructing models to predict the thermal regime of soils. Such information assumes greater importance with increasing attention paid to developing the agricultural industry in University of Ibadan and its environs. Since the early growth and development of a crop may be determined to a large extent by microclimate, the practical significance of knowing the thermal properties of soils under a given set of conditions is most important.
Electrical geophysical methods, on the contrary, allow rapid measurement of soil electrical properties, such as electrical conductivity, resistivity, and potential, directly from soil surface to any depth without soil disturbance. The in-situ methods of electrical conductivity (e.g. four-electrode probe and electromagnetic induction) are routinely used to evaluate soil salinity (Halvorson and Rhoades, 2016; Chang et al., 2013; Rhoades et al., 2019b)
1.2 Statement of the problem
The arrangement of soil particles, particle size, mineralogy, solute concentration, and bulk density affects electrical and thermal conductivities, which are key properties for estimating oil physical states, subsurface water and energy balances, and land-atmosphere interactions.
The purpose of this study was to compare how and A change as a function of water content for soils under different vegetation and with different properties.
1.3 Aim and objectives of the study
The aim of this study is to determine the variability of thermal and electrical properties of a dry sandy soil. The objectives of the study are:
- To study how thermal and electrical properties change as a function of dry soils under different vegetation and with different properties.
- To determine if soils from different states significantly influenced soil thermal or electrical properties across a range of contents.
- To study different properties of dry sandy soil.
1.4 Significance of the study
This study contributes toward improved understanding of soil thermal and electrical conductivities over a range of soils. The study will serve as a means of predict how soil temperatures vary in space and time.
1.5 Scope of the study
The scope of this study covers variability of thermal and electrical properties of a dry sandy soil. The thermal properties was carried out using KD2 Pro which is a fully portable field and laboratory thermal properties analyzer. It uses the transient line heat source method to measure the thermal diffusivity, specific heat (heat capacity), thermal conductivity, and thermal resistivity, while the electrical properties of a dry sandy soil was carried out using Electrical geophysical methods, on the contrary, which allows rapid measurement of soil electrical properties, such as electrical conductivity, resistivity, and potential, directly from soil surface to any depth without soil disturbance.
CHAPTER FIVE
5.0 CONCLUSION AND RECOMMENDATION
5.1 CONCLUSION
The variability of thermal properties over cultivated fields is mainly determined by soil moisture content and bulk density values and their variation which is also modified by meteorological conditions, agricultural treatments and crops. Thermal properties of sandy soils play an important role in influencing the microclimate. These properties influence how energy is partitioned in the soil profile. As regards soil temperature, it is more accurately associated with the transfer of heat throughout the soil, by radiation, conduction and convection. Plants processes such as root growth or germination do not occur until the soil reaches certain temperature depending on the particular plant. Another plant process adversely affected by cold temperature is transport of nutrients and water. A better understanding of how different soils warm up would benefit agriculture by allowing better planning of planting of crops.
From the study, electrical resistivity of Perth sandy soil was found to be independent of the AC input voltage and frequency within the ranges used in this study. The resistivity of the sandy soil decreased rapidly with an increase in water content, but the rate of decrease reduced considerably for water contents over 12% in the case of distilled water and 10% for tap water, irrespective of the relative density. The resistivity showed an almost linear decrease with a corresponding increase in relative density. The effect of varying relative density on resistivity diminished progressively with an increase in water content. The type of permeating fluid used had a significant effect on resistivity whereas the electrode material had a negligible impact on electrical resistivity measurements for the given test duration. For the sandy soils, relative density and water content can be used to predict electrical resistivity and vice versa.
5.2 RECOMMENDATION
It is important to note that the findings reported here should not be extrapolated to soils significantly different from the sandy soil used in this study. Furthermore, the experimental simplifications made in the present study should be kept in mind while using the results reported here in field projects.
